1. Field of the Invention
The present invention relates to a disk driving/recording apparatus having a thin-film head, and more particularly to a method of eliminating a wiggle noise generated by data recording current applied to the thin-film head during the recording operation of data on a magnetic recording medium.
2. Description of the Related Art
Currently, a disk driving/recording apparatus such as a hard disk drive (hereinbelow, referred to as HDD) and a floppy disk drive is widely used as an auxiliary memory device in a computer system. Particularly, among them the HDD has merit in that it can stably store a large quantity of data as well as access the large quantity of data at a high speed. These days, for the HDD, for the purpose of maximization of data storage capacity a track density of a disk or a magnetic recording medium has been continuously increased, which is followed by a trend toward more high head precision. A head used the most widely as high precise head now is a thin-film head on which a core is formed by using a semiconductor technique. The use of the thin-film head may increase data record density, but raise new various problems relating to the property of a head pole. An example of such a manufacturing process is described in U.S. Pat. No. 5,187,860 to Shinji Horibata, et al. entitled Method Of Manufacturing Thin Film Magnetic Head.
A typical one of the above problems is a phenomenon which is called a wiggle noise. This represents a noise generated when the operation mode of the HDD is changed from a record state to a read state.
Now, an explanation on the wiggle noise generation process will be given. When data is recorded a data recording current is applied to a coil of the head and the magnetic polarity of the poles in the head causes a magnetic field to be generated in the gap between the head and the surface of a disk. The magnetization of a magnetic layer of the disk by the generated magnetic field allows data to be recorded on the surface of the disk. Such a data recording operation is accomplished by interrupting the data recording current after all data to be recorded is recorded. Once the data recording current is interrupted, from that moment the arrangement of materials constituting the poles is disorderly, unlike when data are being read as an entropy increases, which causes a variation in the magnetic field. Such a variation in the magnetic field affects the coil of the magnetic head, causing a current component to be produced in the coil, and such a current component is called a an irregular noise due to wiggle phenomenon, also known as a wiggle noise due to a domain pinning phenomenon.
The aforementioned domain pinning phenomenon represents a metastable state of the magnetic head due to unbalance of magnetization, and in this state there has been a problem that the stable data playback operation is not executed since the magnetic head is in an unstable state. U.S. Pat. No. 5,053,892 to Louis Supino, Jr., et al., entitled Thin Film Head Read Recover attempts to solve this conventional problem by repositioning the head over a diagnostic read/write track having no data which is located inside a guard band, when data read error is generated by the domain pinning phenomenon. Then the magnetic head executes a write operation on the diagnostic track. Then the head is repositioned back over the original track from which a data read error was generated to attempt to read data again. The write operation is performed in order to reconfigure the domains and thus return the head to a condition in which it can perform an acceptable read operation. In this case, a latency time for the magnetic head to be repositioned over the diagnostic track and then back over the original track is required, thereby deteriorating the performance of the HDD.
U.S. Pat. No. 5,392,169 to Bernell E. Argyle, et al., entitled Electrical Means To Diminish Read-Back Signal Waveform Distortion In Recording Heads contemplates a method and apparatus for eliminating unfavorable magnetic domain patterns in the head by storing a polarity of the last write current pulse of a write pulse train applied to the head coils, and resetting the head to a magnetic domain state most preferred for a read operation by applying a reset pulse, or pulses, to the head prior to the read operation when the stored polarity of the last write current pulse is determined to be opposite the polarity of a reset current pulse. The reset pulse(s) are applied to the head after the head is either re-positioned over a dedicated track having no data, or, if not re-positioned, only when the head is flying over a sector gap.
A more recent effort to avoid the problems which occur due to the use of thin film magnetic heads and increase disk density has been an effort to replace the thin film magnetic heads with a head using an element utilizing magneto-resistive effect, i.e., a MR head. The use of MR heads also, however, also results in problems occurring due to transitions between read and write states as in a shown by Hidekazu Shibasaki, et al. in U.S. Pat. No. 5,623,378 entitled Signal Reproducing Circuit Adopted For Head Utilizing Magneto-Resistive Effect With Control For Reducing Transient Period Between Read And Write States.